seismic velocity
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On 12th July 1960, a velocity survey of the A.A.O. Pickanjinnie No. 1 bore was made by the Bureau of Mineral Resources. The bore had been drilled to a depth of 5218 ft and was surveyed to the bottom. The average velocities for the Mesozoic rocks and the Timbury Hills Formation are similar to those measured in the Timbury Hill No. 2 bore. However, it seems impossible to correlate individual units within the Mesozoic sequence according to their velocity.
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Following a month of preliminary experimental seismic work in the latter part.of 1964 the Bureau of Mineral Resources carried out a reconnaissance seismic survey of the southern part of the Georgina Basin, mainly in the Northern Territory, from April to October 1965. In most areas reflections proved very difficult to obtain. A number of different techniques were tried, including various shot andgeophone pattern arrangements, noise testing,collinear offset shooting, airshooting and multiple coverage, but no technique was found which was generally successful in providing useful reflections. The seismic results tended to confirm gravity indications that there is a shelf area between BMR 12 Bore and Tobermory and provided no indications that there are deep Palaeozoic troughs similar to the Toko -Syncline in the survey area.
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A deep crustal seismic reflection survey, conducted at Gundary Plains near Canberra, to test a digital seismic recording system, produced additional data for interpretation of seismic refraction profiles in the Lachlan Fold Best. Good reflections were recorded down to the probable Moho, at an estimated depth of 41 km. The intracrustal reflections are characterised by bands of seismic energy, which probably represent velocity transition zones within the crust.
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The Vibroseis method of seismic exploration was first introduced into Australia during 1963. In accordance with the programme for accelerated oil search, the Bureau of Mineral Resources employed a Vibroseis seismic party to demonstrate the performance of the method in various problem areas within the Otway and Sydney Basins, the locations of which are indicated on the regional map. The Experimental Vibroseis Seismic Survey was conducted by Seismograph Service Limited. Party 243. on behalf of the Bureau of Mineral Resources, Geology and Geophysics during the period from 11th May to 3rd October, 1964. The broad objective of the survey was to demonstrate the capabilities of the Vibroseis method in selected areas where previous conventional seismic surveys had experienced difficulties in obtaining results and where various seismic problems had been defined. The main aim of the survey was to obtain good quality results rather than a high production rate yielding poorer quality data. However, as a secondary objective, some short production traverses were recorded USing the optimum field technique developed during the course of the survey for comparison e with normal shot hole production techniques.
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During 1963, the Australian National Antarctic Research Expeditions carried out two over snow traverses in the vicinity of Wilkes Station, Antarctica. The Autumn Traverse reached a point about 100 miles east of Wilkes and the Spring Traverse a point about 300 miles south-east of Wilkes. Surface elevations were measured by barometric methods and ice thicknesses were determined by gravity and seismic techniques. Magnetic measurements were made and borehole temperatures were taken. Experiments were conducted to devise means of improving the quality of the seismic reflection records. The optimum frequency range for the filter settings was found to be 90-215 c/s. A hand-drilled 4-ft shot-hole was adequate in the coastal or low plateau regions within 150 miles of Wilkes. Further inland, a shot hole of at least 30-ft depth was required. The optimum charge size was one pound of explosive.
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The preliminary investigation was made when the Bureaut s seismic party was held up by flooded rivers, while on its way t o Christmas Creek in May, 1954. Results show that the seismic aethod is applicable to the Broome area, and that a sedimentary section of the order of 12,500 feet exists. They further show that a syncline and anticline not known from the surface geology may possibly exist at depth.
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The Bureau of Mineral Resources seismic party carried out a seismic survey in the Bonaparte Gulf area of north-western Australia between 16th June and 13th October, 1956. The initial objects of the survey were to obtain regional information on the thickness of the sedimentary rocks and on the tectonics of the Bonaparte Gulf Basin, and to establish the applicability of the seismic method in the area. During the course of the survey the party was directed to transfer its attentions to obtaining some detailed information on the Spirit Hill Anticline. This latter work was carried out in response to an application by Westralian Oil Pty. Ltd., which was anxious to select sites for a test boring programme. The seismic results indicate a maximum thickness of sediments of about 20,000 feet in the Carlton Basin and 14,000 feet in the Burt Range Basin. The rocks in both these basins have been folded to a considerable extent and the reflections suggest unconformities within both basins. The seismic reflection method proved successful in indicating geological structure at depth in most of the areas tested.
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Geoscience Australia acquired the Papunya Seismic Reflection Survey in 2010. The survey involved the acquisition of high resolution seismic reflection data along a single 11.5km traverse (10GA-PA1). The purpose of the survey was to obtain information on key palaeovalley characteristics for potential groundwater studies. This dataset contains seismic data and images only, a full report on the results of the palaeovalley study can be found in GA Record 2012/09. Raw data for this survey are available on request from clientservices@ga.gov.au
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Geoscience Australia acquired the Boulia Region Deep Crustal Seismic Survey in two stages during 2014 and 2015. The survey involved the acquisition of seismic reflection and gravity data along three traverses, 14GA-CF2 (369km), 14GA-CF3 (339km) and 15GA-CF3 (140km). Traverse CF3 was carried out over two campaigns with a 6km overlap between the two lines. The purpose of the survey was to establish the architecture of the southern Mount Isa Inlier as well as determining the depth of sediment cover over the Proterozoic basement. The project was collaboration between the Geological Survey of Queensland and Geoscience Australia with funding from the Queensland Governments Future Resources (Mount Isa Geophysics) Program. <b>Raw data for this survey are available on request from clientservices@ga.gov.au</b>
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Towa.:ccis the end of 1960 , the Bureau. of Mineral Resources, Geology and Geophysics made a brief seismic survey in the Winton area of Queensland to resolve an apparent contradiction between the interpretations of gravity and aeromagnetic results previously obtained in the area. Gravity and aeromagnetic results both suggested the occurrence of a large fault or fault zone about 20 miles north-west of Winton, but the gravity and aeromagnetic interpretations differed regarding the direction of throw of the fault. A nine-mile seismic reflection traverse was surveyed across the supposed fault. The seismic results indicate the presence of a large fault or monoclinal fold with dowthrown side nouth-wast as suggested by the gravity values and also a smaller fault or monocline about two miles south-east with downthrown side south-east. The variations in thckness of Mesozoic rocks caused by these features were insufficient to explain the observed Bouguer gravity anomaly values, but the seismic results left open the possibilitues that there may be a considerable thickness of pre-Mesozoic sedimemts north-west of the main monocline or fault. It is postulated that the steep gravity gradient observed may be due to a large fault whose main movement took place in pre-Mesozoic times. Indications are that there is 5000 to 6000 ft of Mesozoic sediments in tha area.